A Pasquarelli

Publications of A Pasquarelli

• Open magnetic and electric graphic analysis

  Authors: H.-P. Muller, I. Decesaris, M. Demelis, L. Marzetti, A. Pasquarelli, S.N. Erne, A.C. Ludolph, J. Kassubek

  Engineering in Medicine and Biology Magazine, IEEE. 06/2005;

  In this article, a novel analysis technique, open magnetic and electric graphic analysis (OMEGA), is described and is applied to combine MEG and fMRI measurements in a motor task. The study wasIn this article, a novel analysis technique, open magnetic and electric graphic analysis (OMEGA), is described and is applied to combine MEG and fMRI measurements in a motor task. The study was intended to demonstrate how, within OMEGA, the localization of brain activation can be complemented by integrated analysis of human multimodal functional (MEG, fMRI) and anatomical (MRI) measurements. The OMEGA software provides an analysis platform for user-independent, fast, and reproducible multimodal analysis in one single software environment. The implementation of OMEGA allows the analyst to receive comprehensive MEG/fMRI results in a matter of minutes after the measurements have been completed. With OMEGA, the clinical researcher gets comprehensive information in a quick and standardized approach about the sites and the time course of neurological activation, which is useful for clinical applications and diagnostics.

• Argos 500: operation of a helmet vector-MEG.

  Authors: A Pasquarelli, R. Rossi, M De Melis, L Marzetti, A. Trebeschi, H P Müller, S N Erné

  Neurology & clinical neurophysiology : NCN. 02/2004; 2004:97.

  We here describe the MEG system recently installed at the University of Ulm; it is specifically designed for clinical application and routine use, to allow investigation of a large number of patientsWe here describe the MEG system recently installed at the University of Ulm; it is specifically designed for clinical application and routine use, to allow investigation of a large number of patients per day. To reach this goal, the system design meets the requirements of reliability, high field sensitivity, minimal set-up time before each measurement and an easy-to-handle user interface. The sensor system consists of a 163 vector-magnetometers array oriented and located in a suitable way to cover the whole head of the patient. Four additional triplets are available as references to arrange software gradiometers. The helmet shaped sensor system is positioned to accommodate the patient in a supine position. Simultaneously to the MEG, there are 64 EEG channels. Other relevant patient information can be recorded up to a total number of 660 acquisition channels. Noise level of a single magnetometer is about 5 fT/square root of Hz. Maximum sampling rate is 4200 Hz.

• Multi-channel magnetocardiography for detecting beat morphology variations in fetal arrhythmias.

  Authors: R Sturm, H P Müller, A Pasquarelli, M DeMelis, S N Erné, R Terinde, D Lang

  Prenatal diagnosis. 02/2004; 24(1):1-9.

  OBJECTIVE: Over the last few years, a number of studies have shown that fetal magnetocardiography (fMCG) is useful in describing fetal cardiac activity. A 55-channel MCG system in Ulm was used toOBJECTIVE: Over the last few years, a number of studies have shown that fetal magnetocardiography (fMCG) is useful in describing fetal cardiac activity. A 55-channel MCG system in Ulm was used to record fetal cardiac activity in 12 pregnant women (with normal fetal heart activity in echocardiography) and in 5 pregnant women in whom the echocardiography showed fetal arrhythmias. METHOD: The recorded MCG data were treated in order to eliminate the maternal signal and three MCG channels with the best signals were used to emulate a standard electrocardiogram (ECG) recording so that standard MCG analysis could be performed. RESULTS: The results in assessing fetal electrophysiology, demonstrating its potential, are presented here for two fetuses with recorded supraventricular extrasystoles (SVES) and for one with ventricular extrasystoles (VES). Concerning the SVES, the analysis software OMEGA was able to separate three different beat morphologies. The VES could be detected exactly and have been confirmed by postnatal ECG. CONCLUSION: The beat morphology and the beat-to-beat variations allow new insights into the electrophysiology of the fetal heart.

• Calibration of a vector-MEG helmet system.

  Authors: A Pasquarelli, M De Melis, L Marzetti, H P Müller, S N Erné

  Neurology & clinical neurophysiology : NCN. 02/2004; 2004:94.

  The MEG system Argos 500, recently installed at the University of Ulm, is designed for clinical application and routine use, to allow investigation of a large number of patients per day. To reachThe MEG system Argos 500, recently installed at the University of Ulm, is designed for clinical application and routine use, to allow investigation of a large number of patients per day. To reach this goal, the system design meets the requirements of reliability, high field sensitivity, minimal set-up overhead before each measurement and an easy-to-handle user interface.The sensor system consists of a 163 vector-magnetometer array oriented and located in a suitable way to cover the whole head of the patient. Four additional triplets are available as references to build software gradiometers. To use this system at a high performance level, it must be properly calibrated, with these goals: to determine the actual geometry of the sensors array, which can deviate from the design specifications, and to determine the actual sensitivity of each sensor. The calibrating source consists of 31 coils placed at the corners of a head-size dodecahedron. Various details of the calibration system and process are presented here.

• MSR upgrade for clinical MEG

  Authors: A Pasquarelli, S. N. Ern, A. Trebeschi

  12/2001;

  Introduction To accommodate the new Argos 500 MEG instrument [1] a general upgrade of the existing 2+1layer magnetically shielded room at the neurological department was necessary. Due to theIntroduction To accommodate the new Argos 500 MEG instrument [1] a general upgrade of the existing 2+1layer magnetically shielded room at the neurological department was necessary. Due to the innovative technology and the ambitious goal more stringent requirements where set for shielding performances and shielding anisotropy. The upgrade process of the existing MSR was carried out in cooperation with Advanced Technologies Biomagnetics and consisted in: 1. Adding a third layer of soft magnetic material. 2. Redesigning the structure supporting the magnetic layers of the door to improve the matching with the walls to reduce the door effects. 3. Redesigning completely the operation of the door by removing all hidden mechanisms and leverages and replacing them with external pneumatic locks. 4. Adding extra features like automatic emergency release of the door in case of power and or airpressure failure and manual locks disengage in case of mechanical failure. 2 Methods The Magnetic

• A 165-Channel Neuromagnetometer for Multimodal Brain Imaging

  Authors: V Pizzella, S Della Penna, S. N. Ern, C. Granata, A Pasquarelli, K Torquati, R. Rossi, M. Russo

  12/2001;

  this paper we report about a 165-channel neuromagnetic system developed in an frame of an international multidisciplinary cooperation between the Advanced Biomedical Technologies (ITAB) of thethis paper we report about a 165-channel neuromagnetic system developed in an frame of an international multidisciplinary cooperation between the Advanced Biomedical Technologies (ITAB) of the University of Chieti (Italy), the Central Institute for Biomedical Engineering (ZIBMT) of the University of Ulm (Germany), the Istituto di Cibernetica of the National Research Council of Italy, and the Italian company Advanced Biomedical Technologies (ATB) [1]. This system, shown in figure 1, is installed at ITAB, and it is used in combination with a fMRI SIEMENS VISION 1.5 T system for multimodal brain imaging

• The study of steady magnetic fields associated with primary and secondary ST shift in ischaemic rabbit hearts.

  Authors: E C Monteiro, S Della Penna, L. Di Donato, S Di Luzio, A Pasquarelli, S N Erné, G L Romani

  Physiological measurement. 09/1997; 18(3):191-200.

  The study of injury potentials associated with DC currents that generate the primary or secondary ST shifts during cardiac ischaemia is possible only through the invasive technique of the DCThe study of injury potentials associated with DC currents that generate the primary or secondary ST shifts during cardiac ischaemia is possible only through the invasive technique of the DC electrogram. Clinical surface ECG recordings are AC coupled and cannot be used. This paper reports the use of non-invasive and unshielded magnetocardiographic measurements to evaluate the DC injury currents associated with ST shifts during coronary artery occlusions in the isolated rabbit heart. The effect on the magnetic ST shift is studied under different ischaemic conditions including regional ischaemia, global ischaemia, global ischaemia following long periods of regional ischaemia, regional ischaemia after repeated episodes of reversible global ischaemia, and bilateral regional ischaemia. Recording of DC magnetic fields allows the characterization of primary and secondary ST displacement for each induced ischaemic condition. Our measurements show that the ST shift starts earlier when inducing ischaemia in hearts previously subjected to ischaemic episodes than in hearts where the ischaemia was produced for the first time.

• A SQUID based AC susceptometer for the investigation of large samples.

  Authors: A Pasquarelli, C Del Gratta, S Della Penna, S Di Luzio, V Pizzella, G L Romani

  Physics in medicine and biology. 12/1996; 41(11):2533-9.

  We developed a SQUID based susceptometer with a large available magnetized volume for the investigation of large objects. The magnetizing field is generated by a pair of Helmoltz coils. To achieve aWe developed a SQUID based susceptometer with a large available magnetized volume for the investigation of large objects. The magnetizing field is generated by a pair of Helmoltz coils. To achieve a high signal-to-noise ratio, the susceptometer is operated in a lock-in mode with an AC magnetizing field. A negative feedback control allows the rejection of the applied field with a relative residual of 1 x 10(-7). The apparatus was tested with substances of known magnetic susceptibility. The overall sensitivity, stated in terms of the magnetic moment, is better than 7 x 10(-11) A m2 for small samples.

• Topography and sources of electromagnetic cerebral responses to electrical and air-puff stimulation of the hand.

  Authors: P M Rossini, G Deuschl, V Pizzella, F Tecchio, A Pasquarelli, E Feifel, G L Romani, C H Lücking

  Electroencephalography and clinical neurophysiology. 06/1996; 100(3):229-39.

  SEPs and SEFs after air-puff stimulation of index and little fingers have been studied and compared to the responses following electrical stimulation of the same digits and of the median nerve at theSEPs and SEFs after air-puff stimulation of index and little fingers have been studied and compared to the responses following electrical stimulation of the same digits and of the median nerve at the wrist in 5 subjects. The differences in morphology of the evoked signals are described and the generator characteristics are analysed for SEFs by means of a moving dipole model inside a homogeneous sphere. In our measurements the magnetic fields following electrical finger stimulation show a 30 msec component, which was absent following air-puff stimulation. This could not be seen in the electric field activity. The generators of the first component of SEFs after air-puff finger stimulation proved to be deeper (8 mm on average across all subjects and for both fingers) than in the case of electrically evoked SEFs. A similar behaviour was also observed for the second component of SEFs for the 2 stimulus modalities.

• Analysis of interhemispheric asymmetries of somatosensory evoked magnetic fields to right and left median nerve stimulation.

  Authors: P M Rossini, L Narici, G Martino, A Pasquarelli, M Peresson, V Pizzella, F Tecchio, G L Romani

  Electroencephalography and clinical neurophysiology. 01/1995; 91(6):476-82.

  This paper represents the first neuromagnetic systematic investigation of the asymmetries between the sources activated in the right and left hemispheres after electric median nerve stimulation. WeThis paper represents the first neuromagnetic systematic investigation of the asymmetries between the sources activated in the right and left hemispheres after electric median nerve stimulation. We focused our attention on the location and strength of the equivalent sources activated in the primary somatosensory cortex contralateral to the stimulated nerve in the 50 msec post-stimulus epoch. The spatial coordinates of the equivalent sources did not differ statistically significantly in the two hemispheres. Minor individual asymmetries are shown to be related to the interhemispheric differences in the position of the central sulcus as revealed by MRI investigation. The equivalent sources were significantly stronger in the left hemisphere. When comparing the location of the generators across individuals, we show that interhemispheric differences fluctuate less than absolute values. A quantitative evaluation of these findings is also given. Based on these results, a normative data set has been established, to be used as a baseline in following up changes of interhemispheric asymmetries due to hemispheric lesions and subsequent cortical reorganization.

• Magnetocardiography and exercise testing.

  Authors: K Brockmeier, S Comani, S N Erné, S Di Luzio, A Pasquarelli, G L Romani

  Journal of electrocardiology. 05/1994; 27(2):137-42.

  Twenty healthy male subjects (age range, 15-25 years; median, 21 years) underwent magnetocardiography during physical exercise. Significant ST-segment displacements of the magnetic signal were foundTwenty healthy male subjects (age range, 15-25 years; median, 21 years) underwent magnetocardiography during physical exercise. Significant ST-segment displacements of the magnetic signal were found during exercise at a heart rate of 120 beats/min compared to the magnetic signal at rest (P < .001). Since no significant ST-segment changes were found in the electrocardiogram recorded simultaneously with the magnetocardiogram, it is concluded that the magnetocardiogram shows junctional ST-T segment changes earlier than the electrocardiogram.

• Short-term brain 'plasticity' in humans: transient finger representation changes in sensory cortex somatotopy following ischemic anesthesia.

  Authors: P M Rossini, G Martino, L Narici, A Pasquarelli, M Peresson, V Pizzella, F Tecchio, G. Torrioli, G L Romani

  Brain research. 05/1994; 642(1-2):169-77.

  Transient rearrangements of finger representation in primary somatosensory cortex induced by an anesthetic block of the sensory information from adjacent fingers have been shown invasively inTransient rearrangements of finger representation in primary somatosensory cortex induced by an anesthetic block of the sensory information from adjacent fingers have been shown invasively in animals. Such a phenomenon has been now replicated in seven healthy human volunteers. Somatosensory Evoked Fields (SEFs) have been recorded during separate electrical stimulation of the 1st, 3rd, or 5th finger. Recordings were obtained in control conditions (stage A), following complete ischemic anesthesia of the 4 non-stimulated fingers (stage B), and after regaining sensation (stage C). SEFs were recorded using a 28-channel DC-SQUID magnetometer; a single position of the sensor was enough to identify the source of N20m, P30m and following components using the Equivalent Current Dipole (ECD) model. The amount of afferent input during stages A through C was monitored with surface electrodes placed on the nerve at wrist and elbow. No variation of the nerve compound potential was observed during stages A through C. In stage A, the localizing algorithm was able to discriminate the individual finger representation in accordance with the somatotopic organisation of the sensory homunculus. It was observed that the ECDs responsible for the cortical responses from the unanesthetized finger were significantly changing following a relatively brief period of sensory deprivation from the adjacent fingers. Such changes of the ECDs with respect to the control conditions were characterized by an increase in strength and deepening for the middle finger, and by a shift on the coronal plane for the thumb and the little finger (medial for the former, lateral for the latter). Such changes became progressively evident in stage B, but were persisting in stage C.

• 11 channel magnetometer for biomagnetic measurements in unshielded environments

  Authors: S. Casciardi, C. Del Gratta, S. Di Luzio, G.L. Romani, V. Foglietti, A. Pasquarelli, V. Pizzella, G. Torrioli

  Applied Superconductivity, IEEE Transactions on. 04/1993;

  The authors describe a novel 11-channel magnetometer designed for operation in unshielded environments. The planar geometry of the system is particularly suitable for recording biomagnetic signalsThe authors describe a novel 11-channel magnetometer designed for operation in unshielded environments. The planar geometry of the system is particularly suitable for recording biomagnetic signals over a flat surface, as required for cardiac and gastrointestinal applications. The specific configuration of the sensor array also makes it possible to use the system for reliable and fast cardiac clinical measurements. Ambient noise rejection was achieved by the use of second-order gradiometers, optimized by means of additional fine balancing, whereas a sensitivity of less than 10 fT/Hz^1/2 was obtained by low-noise DC-SQUIDs (superconducting quantum interference devices), using Nb/Nb₂O ₅/PbAuIn technology for the Josephson junctions. The system is presently utilized for a systematic investigation of the localization properties of cardiac sources from data obtained during single-shot measurements, which are believed to be suitable for clinical studies. The results of localization are compared with anatomical information from magnetic resonance imaging data

• Operation of a hybrid 28-channel neuromagnetometer

  Authors: V. Foglietti, A. Pasquarelli, V. Pizzella, G. Torrioli, G.L. Romani, S. Casciardi, W.J. Gallagher, M.B. Ketchen, A.W. Kleinsasser, R.L. Sandstrom

  Applied Superconductivity, IEEE Transactions on. 04/1993;

  A 28-channel system for neuromagnetic measurements operative at CNR-IESS (Instituto di Elettronica dello Stato Solido) is described. The instrument uses 28 Nb/PbAuIn DC-SQUID (superconductingA 28-channel system for neuromagnetic measurements operative at CNR-IESS (Instituto di Elettronica dello Stato Solido) is described. The instrument uses 28 Nb/PbAuIn DC-SQUID (superconducting quantum interference device) sensors coupled with a flux transformer configuration. The detection coils are arranged on concentric circumferences. Sixteen axial first-order gradiometers are arranged in the internal circles, while the external circle consists of 12 first-order planar gradiometers. The vertical gradiometers show a white noise level of &sime;5 fT/√Hz, while the planar ones have a noise &sime;6 fT/cm√Hz, with a 1/ f corner at a few hertz. The evoked potentials of normal subjects and patients affected by various kinds of vascular disturbances have been studied. The system has succeeded at one-shot localization of some cortical activity. The instrument has also been used to record the spontaneous brain activity in patients affected by focal epilepsy

• Measurement of segmental transit through the gut in man. A novel approach by the biomagnetic method.

  Authors: M Basile, M Neri, A Carriero, S Casciardi, S Comani, C Del Gratta, L. Di Donato, S Di Luzio, M A Macri, A Pasquarelli

  Digestive diseases and sciences. 10/1992; 37(10):1537-43.

  The techniques commonly used to evaluate the transit of contents through the gut feature some limitations for being either inaccurate, invasive, inconvenient, or potentially dangerous for theThe techniques commonly used to evaluate the transit of contents through the gut feature some limitations for being either inaccurate, invasive, inconvenient, or potentially dangerous for the subjects. Aim of this study was to establish a safe, noninvasive and accurate technique for the measurement of segmental oroanal transit time. We localized an orally ingested magnetic marker by means of a biomagnetic instrumentation that allows us to identify in a three-dimensional pattern the position of a biomagnetic source inside the body. The biomagnetic localizations were compared with the anatomical data obtained by magnetic resonance imaging investigations. The study was performed in 12 healthy subjects, and scans were taken every hour up to the arrival of the marker into the cecum; thereafter, scans were taken every 4 hr up to the elimination of the marker. In 99% of the isofield maps obtained from each field scan, the marker was localized within the bowel walls. The mean oroanal transit time was 56 +/- 5 hr, the mouth-to-cecum transit time was 13 +/- 1.7 hr, and the total colonic transit time was 43.5 +/- 5 hr (mean +/- SEM). Segmental colon transit did not show major differences among the regions considered, although most of the time was spent in the right colon. In fact, a good correlation was found between transit time through the right colon and oroanal and total colonic transit (r = 0.77, P < 0.02, r = 0.79, P < 0.02 respectively). In conclusion, this method might be a safe alternative to the techniques presently used in the clinical setting for the measurement of intestinal transit.

• Magnetocardiography and exercise testing: data acquisition and data processing

  Authors: K. Brockmeier, S. Comani, S.N. Erne, C. De Gratta, S. Di Luzio, A. Pasquarelli, G.L. Romani

  Computers in Cardiology 1991, Proceedings.; 10/1991

  Sixteen healthy male subjects underwent magnetocardiography during physical exercise. A specific signal averaging technique was developed because the quality of the magnetic signals exceeded that ofSixteen healthy male subjects underwent magnetocardiography during physical exercise. A specific signal averaging technique was developed because the quality of the magnetic signals exceeded that of the electrocardiographic signals, particularly regarding baseline shifting. Significant ST segment displacements of the magnetic signal were found during exercise at a heart rate of 120 bpm ( p <0.001). No significant ST segment changes were found in the electrocardiographic map, which consisted of an array of 16 precordial electrodes, simultaneously recorded. The hypothesis that junctional ST segment displacements can be detected earlier with the magnetocardiogram is discussed

• 28-channel hybrid system for neuromagnetic measurements

  Authors: V. Foglietti, C. Del Gratta, A. Pasquarelli, V. Pizzella, G. Torrioli, G.L. Romani, W.J. Gallagher, M.B. Ketchen, A.W. Kleinsasser, R.L. Sandstrom

  Magnetics, IEEE Transactions on. 04/1991;

  Progress toward the development of a 28-multichannel system for neuromagnetic measurements is described. A novel hybrid design consisting of 16 first-order axial gradiometers and 12Progress toward the development of a 28-multichannel system for neuromagnetic measurements is described. A novel hybrid design consisting of 16 first-order axial gradiometers and 12 first-order planar gradiometers was chosen, which optimize the use of the available cylindrical volume of the dewar tail. This configuration maintains the symmetry of the detected pattern with respect to rotation of a biomagnetic source located under the center of the array and features a localization power considerably better than an array of all first-order planar gradiometers. The detecting array permits simultaneous magnitude measurements over a circular scalp region of 16-cm diameter. The magnetic sensors used are Nb/PbAuIn DC SQUIDs fabricated at IBM. The devices incorporate resonant damping resistors shunting the inductance, resulting in smooth flux-voltage characteristics and, consequently, very low noise figures in a flux-locked loop configuration. A simple and low-cost electronic system has been designed and fabricated for the DC SQUID sensors, consisting of a compact head mounted on top of the cryogenic probe and a control unit where all the DC remote controls are performed. The dynamic range of 10⁷√Hz and the bandwidth of 50 kHz are specifically designed to work in multichannel DC SQUID instrumentation

• Multichannel hybrid system for neuromagnetic measurements.

  Authors: V. Foglietti, C Del Gratta, A Pasquarelli, V Pizzella, G. Torrioli, G L Romani, W.J. Gallagher, M.B. Ketchen, A.W. Kleinsasser, R.L. Sandstrom

  Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft für Medizinische Physik and the European Federation of Organisations for Medical Physics. 02/1991; 12 Suppl B:31-7.

  This paper describes progress toward the development of a 28-multichannel system for neuromagnetic measurements. A novel 'hybrid' design consisting of 16 first-order axial gradiometers and 12This paper describes progress toward the development of a 28-multichannel system for neuromagnetic measurements. A novel 'hybrid' design consisting of 16 first-order axial gradiometers and 12 first-order planar gradiometers was chosen, which optimises the use of the available cylindrical volume of the dewar tail. This configuration maintains the symmetry of the detected pattern with respect to rotation of a biomagnetic source located under the centre of the array and features a localisation power considerably better than an array of all first-order planar gradiometers. The detecting array permits simultaneous magnetic measurements over a circular scalp region of 16 cm diameter. The magnetic sensors used are Nb/PbAuIn DC SQUIDs fabricated at the IBM. The devices incorporate resonant damping resistors shunting the inductance, resulting in smooth flux-voltage characteristics and, consequently, very low noise figures in a flux-locked loop configuration. A simple and low cost electronic system has been designed and fabricated for the DC SQUID sensors.

• Measurement of gastrointestinal transit time by means of biomagnetic instrumentation: preliminary results.

  Authors: M A Macri, M Basile, A Carriero, S Casciardi, S Comani, C Del Gratta, L. Di Donato, S Di Luzio, M Neri, A Pasquarelli

  Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft für Medizinische Physik and the European Federation of Organisations for Medical Physics. 02/1991; 12 Suppl A:111-5.

  The measurement of gastrointestinal transit time, GITT, is of particular interest in the study of gastrointestinal activity and in the diagnosis of some pathologies. In the present work we report theThe measurement of gastrointestinal transit time, GITT, is of particular interest in the study of gastrointestinal activity and in the diagnosis of some pathologies. In the present work we report the measurements of GITT obtained by applying the biomagnetic method.

• Analysis of the ST-segment in terms of principal components: application on multichannel magnetocardiographic recordings.

  Authors: B G Schless, H P Müller, M DeMelis, A Pasquarelli, S N Erné, V Hombach

  Journal of medical engineering & technology. 28(2):56-60.

  Parameterization of the ST-segment is used as a tool for risk stratification for patients to suffer from ventricular tachycardia. This parameterization is performed in terms of Principal ComponentParameterization of the ST-segment is used as a tool for risk stratification for patients to suffer from ventricular tachycardia. This parameterization is performed in terms of Principal Component Analysis (PCA) applied on multichannel magnetocardiographic (MCG) recordings. 55-channel MCG was recorded from 14 normal persons, 10 patients with CHD, 14 patients with MI, and six patients with VT. We found a significantly (p < 0.05) lower PCA-score in patients with MI compared to normals. The lowest PCA-score was found in VT patients. Significant differences can be found between VT patients and normals and also between VT patients and CHD patients.